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[Python-Dev] Enum: subclassing?

Georg Brandl g.brandl at gmx.net
Wed May 1 20:47:19 CEST 2013 
Am 01.05.2013 20:04, schrieb Eli Bendersky:

> Actually, in flufl.enum, IntEnum had to define a magic __value_factory__
> attribute, but in the current ref435 implementation this isn't needed, so
> IntEnum is just:
> 
> class IntEnum(int, Enum):
>     '''
>     Class where every instance is a subclass of int.
>     '''
> 
> So why don't we just drop IntEnum from the API and tell users they should do the
> above explicitly, i.e.:
> 
> class SocketFamily(int, Enum):
>   AF_UNIX = 1
>   AF_INET = 2
> 
> As opposed to having an IntEnum explicitly, this just saves 2 characters
> (comma+space), but is more explicit (zen!) and helps us avoid the special-casing
> the subclass restriction implementation.

Wait a moment... it might not be immediately useful for IntEnums (however,
that's because base Enum currently defines __int__ which I find questionable),
but with  current ref435 you *can* create your own enum base classes with your
own methods, and derive concrete enums from that.  It also lets you have a
base class for enums and use it in isinstance().

If you forbid subclassing completely that will be impossible.

Georg
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